Dual motor strapper

ABSTRACT

A pneumatic strapping tool for tensioning a strap around a load, adhering the strap onto itself, and cutting a feed end of the strap includes a piston, a weld motor operably connected to the piston and a vibrating weld element operably connected to the piston for contacting the strap and adhering the strap onto itself. A tensioning motor is configured for unidirectional rotation. A feed wheel is operably connected to the tensioning motor by a drive assembly to tension the strap prior to adhering the strap onto itself. A transmission cooperates with the drive assembly and is switchable between a first state in which the transmission engages the drive assembly to permit only one-way rotation of the drive assembly and a second state in which the transmission permits two-way rotation of the drive assembly. The strapping tool includes a self-contained pneumatic module that is removably mounted to a cylinder housing. The module includes a compressed gas inlet, a plurality of valves and passageways between the inlet and the valves to provide compressed gas to the cylinder housing, a pneumatic weld motor and the pneumatic tensioning motor. The module includes at least one timer for operation of the weld motor and for providing pressure to the cylinder. An articulating guide is disposed at the strap path and moves between an open path position when the tensioning motor housing is pivoted to the loading/unloading position and a closed path position when the tensioning motor housing is pivoted to the strap engaging position. The guide aligns the strap with a second strap to which the strap it is adhered and aligns the straps with the feed wheel and anvil.

BACKGROUND OF THE INVENTION

The present invention pertains to an improved tool for tightening astrap around an object or load and adhering the strap onto itself. Moreparticularly, the present invention is directed to a dual pneumaticmotor tool for tensioning a strap around a load and welding ormelt-adhering the strap onto itself.

Strapping tools are well-known in the art. These tools come in a widevariety of types, from fully manual tools to automatic, table-top tools.These tools are generally specifically designed for use with metalstrapping or plastic/polymeric type strapping.

Typically, strappers for applying plastic or polymeric strappingmaterials are automatic table-top or hand-held devices. This isgenerally necessary in order to provide energy for adhering thestrapping material onto itself. Typically, the adhering function isprovided by melting or otherwise welding a section of the strappingmaterial onto itself. Such melting or welding operations are generallycarried out using ultrasonic or vibrational-type weld assemblies. Themovement or vibrational motion can be provided by electrical,electromechanical or fluid drive (hydraulic or pneumatic) systems.

In one exemplary tool, a pneumatic system is used to vibrate contactinginterfacial surfaces of overlapping plastic strap portions. The toolincludes a clamping member for anchoring a strap free end portion, and arotatable feed wheel cooperating with an anvil foot to engage a feedstrap portion that is tensioned about the load. A clutch engagablycouples the feed wheel to a pneumatic motor which also vibrates a jawthat welds the overlapping strap portions.

In this single motor arrangement, the motor stalls and tensioning stopsat a specified strap tension. A pneumatically actuated ram disengagesthe motor from the feed wheel and engages the feed wheel break thatmaintains feed wheel tension on the tensioned strap during welding. Sucha tool is disclosed in U.S. Pat. No. 3,564,033 to Angarola et al., whichpatent is assigned commonly herewith, and is incorporated herein byreference. The actuated ram also moves the vibrating jaw into frictionalengagement with the overlapping strap portions. As the vibrating jawmoves toward the overlapping strap portions, a sheering edge severs theupper strap and the overlapping strap portions are subsequently weldedtogether. The pressure is maintained on the welded overlapping strapportions for a cool down period to complete the weld.

Another exemplary tool, disclosed in U.S. Pat. No. 5,380,393 to Drabareket al., also assigned commonly herewith and incorporated herein byreference, discloses a strapping tool having a pneumatic circuit forautomatically controlling tool operation, including the timing andduration of strap welding and the cool down period. A pneumaticallyactuated ram extended after strap tensioning pivots a cam that moves avibrating weld plate into contact with overlapping strap portions toform the weld. Vibration of the weld plate terminates after a timeperiod controlled by the accumulation of air in a chamber. Air issubsequently bled from a cylinder that counter-pivots the ram to movethe welding plate away from the welded strap portions after the cooldown period.

As will be recognized by those skilled in the art, known pneumaticstrapping tools require many system components that increase the sizeand weight of the tool. In addition, even though the pneumatic circuitof the above-mentioned U.S. Pat. No. 5,380,393 automates many strappingoperations otherwise performed manually, controlling timing of thevarious tool operations as relatively and precise, and as a resultinconsistent strap tension and welds may result.

In operation of strapping tools, after tension is applied to the strap,and prior to welding, the tension must be slightly released so that the(welded) strap can be removed from the tool. Otherwise, the tension istypically so high and the foot or anvil is “pinched” so tightly betweenthe strap and the load, that the tool is extremely difficult to removewithout damaging the strap.

In order to accomplish the release or backing-off of the tension, inmany known strapping tools the tensioning motor is reversed or gearingis used to permit roll back of the feed wheel. As such, either the feed(tensioning) motor must be a two-way motor or complex gearing isrequired to carry out the necessary functions of the tool.

Accordingly, there exists a need for a pneumatic strapping tool thatuses two pneumatic motors, one motor for tensioning or feeding strap andanother, separate motor for welding the strap material onto itself.Desirably, such a tool uses one-way or unidirectional pneumatic motors.Most desirably, such a tool has a self contained modular pneumaticmember or module that includes pneumatically controlled timing circuitsand is readily installed onto and removed from the body and motorportions of the tool. Even more desirably, such a tool incorporatesguide elements to properly position and align the strap material betweenthe anvil and the feed wheel to assure optimal strap welding.

BRIEF SUMMARY OF THE INVENTION

A pneumatic strapping tool tensions strap around a load, adhering thestrap onto itself, and cuts a feed end of the strap. The strapperincludes a piston, a weld motor operably connected to the piston and avibrating weld element operably connected to the piston for contactingthe strap and adhering the strap onto itself.

A tensioning motor is configured for unidirectional rotation. A feedwheel rotates about a feed wheel shaft and is operably connected to thetensioning motor by a drive assembly to tension the strap prior toadhering the strap onto itself. A transmission cooperates with the driveassembly. The transmission is switchable between a first state in whichthe transmission engages the drive assembly to permit only one-wayrotation of the drive assembly and a second state in which thetransmission permits two-way rotation of the drive assembly.

In a present embodiment, the drive assembly includes a drive shaft andthe transmission includes a one-way bearing that bears on the driveshaft. The one-way bearing permits one-way rotation of the drive shaftand prevents rotation of the drive shaft in an opposing direction.

The transmission can include a spring clutch engageable with thebearing. The spring clutch, in a first state binds on the bearing toprevent rotation of the bearing relative to the spring clutch. In asecond state, the spring clutch permits rotation of the bearing relativeto the spring clutch.

A release element cooperates with the spring clutch to move the springclutch from the first state to the second state. The release element canbe configured as a collar fitted onto a portion of the bearing adjacentthe spring clutch. The collar includes a finger engageable with an endof the spring clutch to urge the spring clutch to a diameter larger thana diameter when the spring clutch binds on the bearing. The largerdiameter state corresponds to the second state.

In a present strapping tool, the tensioning motor and transmission arecontained within a tensioning motor housing. A release pin is disposedon the housing to traverse through the housing and rotate the collar toengage the spring clutch.

The tool further includes a cylinder housing, a piston disposed within acylinder in the cylinder housing, a pneumatic weld motor operablyconnected to the piston and a vibrating weld element operably connectedto the piston for contacting the strap and adhering the strap ontoitself.

To effect operation of the strapper, the tools includes self-containedpneumatic module that is removably mounted to the cylinder housing. Thepneumatic module including a compressed gas inlet, a plurality of valvesand passageways between the inlet and the valves to provide compressedgas to the cylinder housing, the pneumatic weld motor and the pneumatictensioning motor.

The module also includes at least one timer for operation of the weldmotor and for providing pressure to the cylinder. A part or portion ofan accumulator for controlling timing of the weld motor is formed in themodule, and the other part or portion of the accumulator is formed inthe cylinder housing.

The tool further includes a tensioning piston mounted in part in thecylinder housing. The tensioning piston is actuated by compressed gasfrom the pneumatic module when the pneumatic tension motor is actuated.The tensioning piston acts against the tensioning motor housing when thetool is operating in the tensioning mode.

The pneumatic module includes a tensioning motor valve for controllingcompressed gas flow to the tensioning motor and a weld cycle valve forcontrolling compressed gas flow to the weld motor and piston. Thetensioning motor valve and the weld cycle valve are operableindependently of one another.

A pilot valve is configured to initiate and terminate flow of compressedgas to the tensioning motor valve and the weld cycle valve, that is, tothe pneumatic module.

In a present embodiment, the module includes a tensioning motor valveactuated by a tensioning motor valve switch, for providing compressedgas flow to the pneumatic tensioning motor when the tensioning motorvalve is in an on position. The module further including a weld cyclevalve for providing compressed gas flow to the pneumatic weld motor andto the cylinder through a first pneumatic timer. Compressed gas flow isfurther provided to the accumulator through a second timer. Whencompressed gas pressure in the accumulator reaches a predeterminedvalue, a pressure is applied to the pilot valve to close the pilot valveand to terminate compressed gas supply to the weld cycle valve. Pressureis vented from the cylinder through the second pneumatic timer tocontrol cool down of the strap following welding.

In another aspect of the invention, an articulating guide is disposed atthe strap path. The guide pivots about the feed wheel shaft between anopen path position and a closed path position.

In the open path position, that is when the tensioning motor housing ispivoted to the loading/unloading position, the guide moves upwardly topermit inserting a strap between the feed wheel and anvil. In the closedpath position, that is when the tensioning motor housing is pivoted tothe strap engaging position, the guide blocks insertion of the strapbetween the feed wheel and the anvil and aligns the strap with a secondstrap to which the strap is to be adhered. The guide is furtherconfigured to align the strap and the second strap with the feed wheeland anvil for tensioning. To align the straps the guide includes adepending finger for movement in to and out of the strap path.

To effect articulation, the guide includes an elongated slot and thestrapping tool includes a pin extending therefrom for engaging the slot.The pin is fixed relative to the pivotal movement of the tensioningmotor housing. The pin engages the slot to pivot the guide between theopen path position and the closed path position. The finger can beformed in a plane spaced inwardly of a plane of the guide to urge thestrap toward the feed wheel and anvil when the finger is in the closedpath position.

A feed wheel cover includes a notch formed therein for receiving aportion of the guide when the guide is pivoted to the closed pathposition. The notch maintains the guide laterally in place relative tothe feed wheel.

These and other features and advantages of the present invention will beapparent from the following detailed description, in conjunction withthe appended claims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The benefits and advantages of the present invention will become morereadily apparent to those of ordinary skill in the relevant art afterreviewing the following detailed description and accompanying drawings,wherein:

FIG. 1 is a perspective view of a dual pneumatic motor strapperembodying the principles of the present invention, the tool being shownwith a strap material positioned in the tool, and showing the directionof movement of the material during tensioning;

FIG. 2 illustrates the tool positioned relative to a load being strappedand the direction of movement of the strap material during tensioning;

FIG. 3 is a side view of the strapping tool shown in the operating orengaged position in which the fed wheel engages the strap material;

FIG. 4 is a partial, enlarged view of the feed wheel and anvil withstrap material engaged therebetween, and showing the “roll-back” of thefeed wheel following tensioning and welding, at release;

FIG. 5 is a side view of the strap positioned between the anvil and feedwheel as illustrated in FIG. 4;

FIG. 6 is a side view of the strapping tool similar to FIG. 3, butshowing the tool in the release or loading/unloading position to loadstrap material into the strapper tool and to remove the strap materialafter it has been welded onto itself;

FIG. 7 is an exploded view of the strapping tool;

FIG. 8 is a partially exploded, partially cut-away view of thetensioning motor;

FIG. 9 is a cross-sectional view of the assembled motor taken along 9—9of FIG. 8;

FIG. 10 is a partial cross-sectional view of the motor taken along line10—10 of FIG. 9;

FIG. 11 is a partial view of the lower area of FIG. 10 showing therelease plunger engaging the motor inner sleeve to release the springclutch;

FIG. 12 is a cross-sectional view of the self contained pneumatic moduletaken along line 12—12 of FIG. 7; and

FIG. 13 is a schematic view of the self contained pneumatic module.

DETAILED DESCRIPTION OF THE INVENTION

While the present invention is susceptible of embodiment in variousforms, there is shown in the drawings and will hereinafter be describeda presently preferred embodiment with the understanding that the presentdisclosure is to be considered an exemplification of the invention andis not intended to limit the invention to the specific embodimentillustrated.

It should be further understood that the title of this section of thisspecification, namely, “Detailed Description Of The Invention”, relatesto a requirement of the United States Patent Office, and does not imply,nor should be inferred to limit the subject matter disclosed herein.

Referring now to the figures and in particular to FIGS. 1 and 2, thereis shown a dual pneumatic motor strapper or strapping tool 10 embodyingthe principles of the present invention. The tool 10 is configured totension a strap S around a load L, weld the strap material S onto itselfand sever a feed end F of the strap S. For purposes of the presentdisclosure, the strap material S will be referred to as having a feedend F which is the supply end of the material and a free end R which isthat end of the material that is fed around the load L and reinsertedinto the strapping tool 10.

The tool 10 includes, generally, a body 12, a foot 14, a tensioningmotor 16 and housing 18, a weld motor 20, a cylinder housing 22 and apneumatic module 24. The tool 10 can include a handle 26 and grip 28,such as those shown for ease of handling and use. The pneumatic module24, as will be discussed in more detail below, is mounted to thecylinder housing 22 which is in turn mounted to the body 12 and providespneumatic pathways between the module 24, the cylinder housing 22 andthe tensioning and welding motors 16, 20 for introducing and venting acompressed gas, such as compressed air, to and from the motors 16, 20.The module 24 is readily mounted to and removed from the housing 22 by aplurality of fasteners 30 such as bolts and the like.

Referring now to FIG. 7, the welding motor 20 is mounted to the body 12in stationary relation so that the welding motor 20 and body 12 arefixed relative to one another. A weld motor shaft 32 extending from themotor 20 engages an eccentric element 34. The eccentric element 34 ispositioned in an elongated opening 36 in an arm 38 that is operablyconnected at one end to a weld element 40 and at an opposing end to apiston 42. The piston 42 is positioned in the cylinder housing 22.

Upon actuation of the weld motor 20, the shaft 32 rotates which in turnrotates the eccentric element 34. The eccentric 34 is fitted into theelongated opening 36 so that as the motor 20 rotates, it impartsvibrational movement to the weld element 40. The upper and lower straplayers S_(U), S_(L) are positioned between the weld element 40 and astationary weld pad 44 on the foot 14. The vibrational movement istransferred into the strap layers S_(U), S_(L) and welds the strap ontoitself. The operation and construction of such vibrational weld elements40 and the various arrangements to impart vibrational energy will berecognized and understood by those skilled in the art and are within thescope and spirit of the present invention.

To assure that sufficient pressure is exerted by the weld element 40,the piston receives compressed at the top of the piston 42 in thecylinder 46 when the tool 10 is in the welding cycle. The air forces thepiston 42 downwardly to assure that the proper force is exerted on thestrap S as the weld element 40 vibrates.

The foot 14 is likewise mounted to the body 12 so that foot 14 and body12 are stationary relative to one another. The foot 14 includes an anvil48 against which the strap S is held for tensioning. As set forth above,the weld pad 44 is positioned on the foot 14 to maintain a lower sectionof the strap S_(L) stationary as an upper section of strap S_(U) isvibrated to effect the weld.

The tensioning motor 16 is mounted in fixed relation to the tensioningmotor housing 18 which is in turn pivotally mounted to the body 12 by apivot pin 50. The pin 50 permits the motor housing 18 to pivot about anaxis A₅₀. Gearing, indicated generally at 52, located within the housing18 transfers the driving force from the motor 16 to a feed wheel shaft54 on which a feed wheel 56 is mounted. As such, the feed wheel 56pivots along with the tensioning motor 16 and housing 18 about the axisA₅₀.

The feed wheel 56 is positioned within a cover member 58. An end 60 ofthe feed wheel shaft 54 is secured in a sleeve 62 in the cover 58. Aplate 64 extends over the cover 58 to secure the cover 58 to the body12. In this manner the cover 58 pivots with the tensioning motor 16 andhousing 18 (and feed wheel 56) while the plate 64 remains fixed to thebody 12. The cover 58 prevents the feed wheel 56 from lateral movement.

The gearing 52 within the housing 18 for translating movement of themotor 16 to the feed wheel 56 includes a spiroid pinion (not shown)mounted to the motor shaft 68 and a spiroid gear (not shown) mounted tothe feed wheel shaft 54 to translate the rotational movement ninetydegrees from the motor 16 to the feed wheel 56. Such an arrangement, aswell as other arrangements will be readily recognized and appreciated bythose skilled in the art and are within the scope and spirit of thepresent invention.

The tensioning motor 16, as set forth above, is configured for one-wayor unidirectional movement, as indicated by the rotational arrow at 72,when actuated by compressed air. It is, however, also configured topermit a slight “slip” in an opposite direction to accommodate the rollback necessary for releasing tension in the strap S to permit removingthe tool 10 from the load L after the welding operation.

Referring now to FIGS. 8-11, unlike known strappers, the presentstrapper 10 uses a transmission assembly 74 that includes, generally, aone-way bearing 76, a spring clutch 78 and a release element 80, such asthe exemplary movable collar or ring to accomplish the roll back. Themotor shaft 68 is enveloped by or resides within the transmissionassembly 74. The one-way bearing 76 is positioned around the shaft 68and permits the shaft 68 to rotate in one direction, i.e., the drivingdirection 72 only. The bearing 76 includes a plurality of rollers 82within a sleeve 84. The sleeve 84 remains stationary while the rollers82 rotate to provide for smooth rotation of the shaft 68, and to preventlateral shaft 68 movement. Those skilled in the art will recognize andunderstand the construction of such a one-way bearing 76.

The wrap spring clutch 78 is fitted over a portion of the bearing sleeve84. The spring clutch 78 is formed as a coil spring having first andsecond ends 86, 88. The spring first end 86 is secured in a spring seat90. The spring second end 88 lies along the coil periphery. The spring78 has a relaxed state, that is a state in which the spring 78 isneither tensioned, compressed nor torqued (e.g., twisted). In therelaxed state, the spring 78 defines a diameter. When the spring 78 isin an other than relaxed state, such as when the spring 78 is torqued ortwisted, the diameter changes, for example, increases.

The spring clutch 78 is positioned over a portion of the bearing sleeve84 to bind on the sleeve 84 when the spring 78 is in the relaxed state,thus preventing movement of the bearing sleeve 84 relative to the spring78. When the spring 78 is torqued or twisted, the diameter increases toallow the sleeve 84 to “slip” relative to the spring 78. It is thisslippage that provides the roll back required to reduce the strap Stension.

To accomplish the twisting of the spring 78, the transmission includes acollar 80 that is fitted onto the bearing sleeve 84 abutting the spring78. The collar 80 includes a finger or projection 92 extendinglongitudinally from an edge of the collar 80. While the collar 80 abutsthe end coil of the spring 78, the finger 92 is configured to abut thesecond end 88 of the spring 78. In this manner, when the collar 80 isrotated, the finger 92 is urged against the end 88 of the coil to twistthe spring 78. This, in turn, permits the bearing sleeve 84 (and theshaft 68) to rotate backward relative to the spring 78.

The transmission 74 is contained within an outer sleeve 94 that extendsover the spring clutch 78 and collar 80 which are positioned over thebearing 76. A first end 96 of the outer sleeve 94 is open to the motor16 and an opposing or second end 98 of the outer sleeve 94 has anopening 100 therein for the motor shaft 68 to pass through. The outersleeve 94 is positioned within the tensioning motor 18 housing andfixedly mounted therein by a plurality of fasteners (not shown) thatextend through the housing 18 and into the outer sleeve 94.

With reference now to FIGS. 10 and 11, in order to release the bearing76 (i.e., torque the spring clutch 78), as set forth above, the collar80 must be urged or rotated slightly so that the finger 92 contacts andmoves the end 88 of the coil 78. To effect this slight rotation, thehousing 18, outer sleeve 94 and collar 80 include openings 104, 106 and108, respectively, therein. The housing opening 104 and outer sleeveopening 106 are fully aligned with one another. The collar opening 108,however, is slightly out of alignment with the housing and sleeveopenings 104, 106 when the spring 78 is in the relaxed state. By movingthe collar opening 108 into alignment with the other openings 104, 106,i.e., by slight rotation of the collar 80, the finger 92 urges againstthe end 88 of the spring coil 78, to twist or torque the coil 78 andrelease the bearing 76.

A release pin or plunger 110 and release handle 112 (FIG. 7) are mountedto the housing 18 such that the plunger 110 is disposed in the housingand sleeve openings 104, 106 when it is depressed. The plunger 110 ismounted for movement into the openings 104, 106, 108. The plunger 110includes a tapered head 114 that contacts the side of the collar opening108 and rotates or cams against the collar opening 108 to effectrotation of the collar 80 and release of the bearing 76 and shaft 68.

Referring again to FIG. 7, the release handle 112 is mounted to thehousing 18, overlying the plunger 110 to maintain the plunger 110 in theopenings 104, 106, 108 and to provide leverage to force or urge theplunger 110 inward to contact and align the collar opening 108. Thehandle 112 is biased outwardly by, for example, the exemplary handlespring 116. The handle spring 116 bias is readily overcome by grippingthe handle 112, grip 28 and motor housing 18 and squeezing the handle112 inward. The plunger 110 is mounted to the handle 112 by a pin 118 orthe like so that as the handle 112 is released, it pulls the plunger 110out of the collar opening 108.

In addition, when the handle 112 is released, the force of the springclutch 78 against the collar finger 92 rotates the collar opening 108out of alignment with the housing and sleeve openings 104, 106, thusfurther assisting in urging the plunger 110 outward. This action, i.e.,removing the plunger 110 from the collar opening 108, permits the springclutch 78 to return to the relaxed state, which in turn locks thebearing 76 within the spring clutch 78, preventing rearward rotation ofthe shaft 68 and feed wheel 56.

As set forth above, the tensioning motor 16, motor housing 18 and feedwheel 56 pivot between an engaged position (shown in FIG. 3) in whichthe feed wheel 56 rests on the anvil 48 (during strapping operations)and a loading/unloading position (FIG. 6) in which the feed wheel 56 ispivoted away from the anvil 48 to permit inserting or removing the strapS material from between the feed wheel 56 and anvil 48.

To assist in aligning the strapping material between the feed wheel 56and anvil 48, the strapper 10 includes an articulating guide 120. Theguide 120 is configured to assure that the upper layer of strappingmaterial S_(U) fully overlies the lower layer S_(L) of material, andfurther assures that both the upper and lower layers S_(U), S_(L) arepositioned fully under the feed wheel 56 and above the anvil 48.

The guide 120 is mounted to the tool 10 by an opening 122 in the guide120 through which the feed wheel shaft 54 traverses and a slottedopening 124 in the guide 120 through which a pivot pin 126 (extendingfrom the feed wheel cover plate 64) extends. Thus, as the tensioningmotor housing 18 (and thus the feed wheel 56) is pivoted to theloading/unloading position, the guide 120 articulates or pivots. The pin126 extending through the guide slot 124 articulates the guide 120 sothat an aligning finger 128 moves upwardly out of the strap entry way,as indicated at 130. When the motor housing 18 is released to return tothe engaged position, the guide 120 pivots downwardly to position thefinger 128 in the entry path 130 which aligns the upper layer of strapmaterial S_(U) on the lower layer of material S_(L). As best seen inFIG. 7, the aligning finger 128 extends downwardly and inwardly to“push” any misaligned strap between the feed wheel 56 and the anvil 48.

Referring now to FIGS. 7 and 12-13, the pneumatic module 24 is removablymounted to the cylinder housing 22. The module 24 includes a pluralityof components (e.g., switches, valves, accumulators) to control theoverall operation of the strapper 10. The module 24 is configured toreadily mount to and be removed from the housing 22 by, for example, theexemplary bolts 30 (FIG. 1). In this manner, in the event thatmaintenance is required on the pneumatic module 24, the module 24 can beremoved and a replacement module 24 can be readily installed on the tool10 for continued use.

Referring to FIG. 13, a pneumatic schematic is shown. Air enters thetool 10 through a compressed air supply 134 and enters a pilot valve136. The pilot valve 136 is two position valve (on-off) that is biasedto the on position (as shown). The on position routes air to a juncture138 at which the air supply splits with one branch 140 routing air to atension motor valve 142 and the other branch 144 routing air to a weldcycle valve 146.

Depressing or actuating a tensioning motor switch 148 moves thetensioning motor valve 142 into the open position, routing air through avariable orifice 149 to the tensioning motor 16 and routing air to atensioning piston 150. The variable orifice 149 is adjustable to providecontrol of the tensioning motor 16 power output. (Note that thetensioning motor valve 142 is shown in the off or closed position.) Thepiston 150 extends downwardly from the cylinder housing 22 and applies aforce against the tensioning motor housing 18 when the tensioning motor16 is actuated. The piston 150 provides an assist to the spring force ofthe tool 10 to the engaged position. A spring 152 is positioned abovethe piston 150 to bias the piston 150 downwardly against the motorhousing 18. Releasing the tensioning motor switch 148 closes thetensioning motor valve 142, terminating the air feed to the tensioningmotor 16 and to the piston 150.

As set forth above, depressing the tensioning motor switch 148 actuatesthe tension motor 16 which rotates, driving the drive shaft 68, which inturn rotates the feed wheel 56 to tension the strap S. When apredetermined tension is reached, the motor 16 stalls, and rotation ofthe feed wheel 56 ceases. Releasing the switch 148 merely stops the feedof air to the motor 16. Because of the transmission 74 configuration,i.e., the one-way bearing 76, the shaft 56 cannot rotate backward (thatis to relieve tension on the strap S), even though the force exerted bythe tensioned strap S tends to rotate the feed wheel 56 rearwardly.

A weld cycle switch 154 operates the weld cycle valve 146. Depressingthe switch 154 moves the valve 146 to the on position. (Note that thevalve 146 is shown in the off or closed position.) The weld cycle valve146 is a contact or maintain valve. In the on position, air is routedthrough the second line branch 144 to the valve 146. Air enters thevalve 146 and is routed to the weld motor 20. A line tee 156 from theweld motor line 144 is routed back to the weld cycle valve 146 to “hold”the valve 146 in the on position. The valve 146 is biased to the closedposition, however, the air pressure “holding” the valve 146 open issufficiently high to overcome the spring force.

At the same time that air is routed to the weld motor 20, air isdirected to a volume chamber or accumulator 158, through a weld timer160 and check valve 162 for weld timing. The weld timer 160 is a checkvalve 164 in parallel with a restriction device such as the illustratedorifice 166. In this manner, air flow into the accumulator 158 isrestricted (and thus timed) in that flow through the orifice is limitedor restricted. A line 168 from the accumulator 158 is routed to thepilot valve 136, so that as the pressure in the accumulator 158increases, air flows to the pilot valve 136. When the air in theaccumulator 158 reaches a predetermined pressure, the pilot valve 136closes, thus stopping air flow to the weld cycle valve 146. This stopsoperation of the weld motor 20.

When air flow is terminated to the weld cycle valve 146, the pressureexerted to maintain the valve open (through line 156) also drops, andthe valve 146 returns to the closed position by action of the bias.

Returning to the weld cycle, as air is provided to the weld motor 20,air is also routed to the weld cylinder 46 (to the top of the piston) tomaintain pressure on the piston 42 (which assures that sufficientpressure is applied by the weld element 40 on the strap S). The air isrouted to the top of the weld cylinder 46 through a cool down timer 170.As set forth above, after welding is complete, the strap S must beallowed sufficient time to cool assure the integrity of the weld. Cooldown is accomplish with pressure applied by the weld element 40 on thestrap S (pressure on the piston 42), without the vibrational motion ofthe element 40 being imparted.

The cool down timer 170 maintains pressure on the piston 42 withoutvibrational motion of the weld element 40. When the air to the weldmotor 20 is stopped, the weld element 40 ceases to vibrate. The airrouted to the top of the weld cylinder 46 is slowly vented from thecylinder 46 by a restricted vent path from the top of the cylinder 46.The cool down timer 170 is configured similar to the weld timer 160 andincludes a check valve 172 in parallel with a restriction device such asan orifice 174. In this manner, although the weld motor 20 has stopped,the pressure exerted by the (piston 42 and the) weld element 40 ismaintained and is slowly released by the timed venting from the cylinder46.

A cutter 176 is mounted to move downwardly into the strap upper layerS_(U) along with the weld element 40. The cutter 176 is mounted to theweld piston 42 by a spring 178 so that the force exerted on the strap Sis variable, to assure that the top layer of strap S_(U) is cut, but toalso prevent cutting into lower layer of strap material S_(L).

Completing the pneumatic circuit, the accumulator 158 is vented throughthe weld cycle valve 146 when the valve 146 is in the off position. Thevent is closed when the valve 146 is in the open position. Those skilledin the art will recognize and understand that the various references to“lines”, “vent paths” and the like are provided by a plurality ofopenings formed, e.g., machined, in the module 24, as shown generally inFIG. 12.

In operation, strap S is fed around the load L with the free end Rpositioned as the lower layer of strap S_(L) and the feed end Fpositioned as the upper layer of strap S_(U). The strap S is fed intothe strapper 10 with the strapper in the loading/unloading position (thetensioning motor housing 18 pulled upward). Both layers S_(U), S_(L) areproperly positioned in the strapper 10, and the motor housing 18 isreleased to move to the tool 10 to the engaged position. With the motorhousing 18 released, the guide 120 moves downwardly to align the strapmaterial layers S_(U), S_(L).

The tensioning motor switch 148 is depressed (moving the tensioningmotor valve 142 to the on position) which actuates the tensioning motor16 and the tensioning piston 150. The motor 16 rotates which in turnrotates the feed wheel 56 tensioning the strap S. When a predeterminedtension is reached, the motor 16 stalls. The tensioning motor switch 148is then released which terminates air flow to the motor 16 and to thepiston 150. The strap S is, however, held securely by the feed wheel 56which is prevented from rotating rearwardly by the transmission 74(i.e., the one-way bearing 76).

The weld cycle switch 154 is then depressed to move the weld cycle valve146 to the on position. As set forth above, this is a contact ormaintain type switch. Compressed air is routed to the valve 146(bypassing the tensioning motor valvel 142), and is routed to the weldmotor 20, to the weld cylinder 46 (through the cool down timer 170), tothe accumulator 158 (through the weld timer 160), and to the valve 146to maintain the valve 146 open. The weld piston 42 is forced downwardlyonto the strap S and the motor 20 is actuated to form the weld. At thesame time, the strap upper layer S_(U) is cut by the cutter 176 (whichis moved into contact with the strap upper layer S_(U) by the piston42). As pressure in the accumulator 158 reaches a predetermined value(by passage of air though the weld timer 160), the pilot valve 136closes thus terminating the flow of air to (and in turn from) the weldcycle valve 146.

When air flow is terminated from the weld cycle valve 146, the motor 20stops and the valve 146 returns to the off position by action of thebias 184 (spring). Weld cylinder 46 pressure slowly decreases by ventingthrough the cool down timer 170. As pressure in the cylinder 46decreases, the piston spring 182 returns the piston 42 to the homeposition, moving the weld element 40 and cutter 176 from the strap S.

The release handle 112 is then gripped moving the plunger 110 into thecollar opening 108 to cam against the collar 80 and effect release ofthe drive shaft 68 and feed wheel 56. This reduces the tension in thestrap S to permit removing the tool 10 from the welded strap S and loadL.

All patents referred to herein, are hereby incorporated herein byreference, whether or not specifically do so within the text of thisdisclosure.

In the present disclosure, the words “a” or “an” are to be taken toinclude both the singular and the plural. Conversely, any reference toplural items shall, where appropriate, include the singular.

From the foregoing it will be observed that numerous modifications andvariations can be effectuated without departing from the true spirit andscope of the novel concepts of the present invention. It is to beunderstood that no limitation with respect to the specific embodimentsillustrated is intended or should be inferred. The disclosure isintended to cover by the appended claims all such modifications as fallwithin the scope of the claims.

1. A pneumatic strapping tool for tensioning a strap around a load,adhering the strap onto itself, and cutting a feed end of the strap,comprising: a piston; a weld motor operably connected to the piston; avibrating weld element operably connected to the piston for contactingthe strap and adhering the strap onto itself; a tensioning motorconfigured for unidirectional rotation; a feed wheel; a drive assemblyoperably connecting the tensioning motor to the feed wheel to tensionthe strap prior to adhering the strap onto itself; and a transmissioncooperating with the drive assembly, the transmission being switchablebetween a first state in which the transmission engages the driveassembly to permit only one-way rotation of the drive assembly and asecond state in which the transmission permits two-way rotation of thedrive assembly, wherein the drive assembly includes a drive shaft andthe transmission includes a one-way bearing that bears on the driveshaft to permit one-way rotation of the drive shaft and to preventrotation of the drive shaft in an opposing direction.
 2. The strappingtool in accordance with claim 1 including a spring clutch engageablewith the bearing, the spring clutch, in a first state binding on thebearing to prevent rotation of the bearing relative to the springclutch, and in a second state permitting rotation of the bearingrelative to the spring clutch.
 3. The strapping tool in accordance withclaim 2 including a release element cooperating with the spring clutchto move the spring clutch from the first state to the second state. 4.The strapping tool in accordance with claim 3 wherein the releaseelement is a collar fitted onto a portion of the bearing adjacent thespring clutch.
 5. The strapping tool in accordance with claim 4 whereinthe collar includes a finger engageable with an end of the spring clutchto urge the spring clutch to a diameter larger than a diameter when thespring clutch binds on the bearing.
 6. The strapping tool in accordancewith claim 5 wherein the tensioning motor and transmission are containedwithin a tensioning motor housing and wherein a release pin is disposedon the housing to traverse through the housing and rotate the collar toengage the spring clutch.